Anja I have been doing a lot for a very long time on this issue. But going on what is being shown on the media - and attending a demonstration only tells you about one demonstration, not all, I think much of the thinking behind these demonstrations strikes me as vacuous.
The simplest way to meet the calls being made at these demonstrations is to turn all our gas and bio mass power stations off immediately, let us see how we manage. Currently, on a windy day, like today, wind power is meeting a third of our power demand, yesterday it was 20%, the day before 3%.
If you are going to demonstrate for something like this, you need a coherent set of suggestions about how to achieve your goal. I have yet to see a single policy document or anything similar from Greta Thunberg and her (adult) supporters.